               (sql/where {:exercises_id (:id exercise)})
               (sql/with entities/ratings (sql/with entities/users))))
 
-(def summarize (comp summarize-rating-sets normalized-rating-sets rating-sets))
+(def summarize (comp summarize-rating-sets normalize-rating-sets rating-sets))

    set
    (create user-id exercise-id)))

(defn normalized-rating-sets 
  "Take a collection of rating sets, normalize the ratings of each set,
   and return a single collection comprising all the normalized ratings."
  [rating-sets]

(defn aggregate-ratings 
  "Given collection of ratings, take their average."
  [ratings]
  (let [summed-rating (reduce fold-sum ratings)
        count (count ratings)
        ratings-average (update-in summed-rating [:rating] #(/ % count))]
    ratings-average))

(defn summarize-rating-sets 
  "Take a collection of ratings, group them by user,
